Input devices that control cursor movement of a computer system are also known as pointing devices, and include mice, trackballs and touch pads. These pointing devices are generally designed for hand use. There are a number of users with various physical disabilities that are unable to use a hand-operated computer input device. The use of a hand-operated computer input device is also problematic for restrictive environments and tasks that need both hands to be completely dedicated to a specific operation other than using the computer input device.
In lieu of hand-operated computer input devices, mouth-operated computer input devices are available. For example, U.S. Pat. No. 6,222,524 to Salem et al. discloses a mouth-operated computer mouse in which a pressure sensitive isometric joystick is used to perform cursor control. The shaft of the joystick points downwards and inwards towards the tip of the user's tongue. The shape of the shaft is conical so as to facilitate a greater ability of the tongue to manipulate the shaft from all directions. Applying varying amounts of force to the joystick changes the speed of cursor movement in the desired direction. Since speed and direction, not position, are the only controls on the cursor, skill must be developed to navigate the cursor to, and stopping on the desired target. A disadvantage of this system is that the necessary tongue activation for moving the cursor is too imprecise. The cursor will continually “hunt” for the target in a series of diminishing overshoots.
Another mouth-operated computer input device is provided in U.S. Pat. No. 7,071,844 to Moise, which discloses a curved housing shaped to closely engage the roof of the user's mouth against the front teeth. A touch pad is arranged on the bottom of the housing, and is operated by the user's tongue for controlling a cursor on a computer display. The touchpad comprises an XY array of pressure sensitive wires. As the tongue moves across the touchpad, the wires in the array that are contacting each other allow the computer system to calculate the direction and distance the tongue has moved from its original location. The pressure “footprint” of the tongue is large compared to that of a fingertip and increases with increased pressure. However, the area available in the mouth for an adequate size XY array is limited. As a result, repetitive tongue swipes are required to move the cursor any appreciable distance.